65 research outputs found
Mapping the distributions of Pacific and western brook lampreys along the Oregon south coast using eDNA and community science : ... report
No full textShon Schooler, Jenni Schmitt, Deborah Rudd, Becky Flitcroft, and Ian Rodger.This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographic references.USDA U.S. Forest Service provided funding for this projectMode of access: Internet from the Oregon Government Publications Collection.Text in English
Status of the European green crab, Carcinus maenas, (aka 5-spine crab) in Oregon estuaries, report for 2022
No full textSylvia Behrens Yamada (Integrative Biology, Oregon State University), Cameron Royer (Integrative Biology, Oregon State University), Shon Schooler (South Slough National Estuarine Research Reserve), Rebecca Flitcroft (Pacific Northwest Research Station, Corvallis Forestry Sciences Lab), Mitch Vance (Oregon Department of Fish and Wildlife), Andrea Randall, Jennifer Fisher (NOAA Fisheries - NWFSC Hatfield Marine Science Center) ; report prepared for: Stephen H. Phillips (Program Manager, Aquatic Nuisance Species Project), Pacific States Marine Fisheries Commission.Title from PDF title page (viewed on April 17, 2023).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographical references (pages 17-19).Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Wide bandgap collector III-V double heterojunction bipolar transistors
No full textThis thesis is devoted to the study and development of Heterojunction Bipolar Transistors (HBTs) designed for high voltage operation. The work concentrates on the use of wide bandgap III-V semiconductor materials as the collector material and their associated properties influencing breakdown, such as impact ionisation coefficients. The work deals with issues related to incorporating a wide bandgap collector into double heterojunction structures such as conduction band discontinuities at the base-collector junction and results are presented which detail, a number of methods designed to eliminate the effects of such discontinuities. In particular the use of AlGaAs as the base material has been successful in eliminating the conduction band spike at this interface. A method of electrically injecting electrons into the collector has been employed to investigate impact ionisation in GaAs, GaInP and AlInP which has used the intrinsic gain of the devices to extract impact ionisation coefficients over a range of electric fields beyond the scope of conventional optical injection techniques. This data has enabled the study of ''dead space'' effects in HBT collectors and have been used to develop an analytical model of impact ionisation which has been incorporated into an existing Ebers-Moll HBT simulator. This simulator has been shown to accurately reproduce current-voltage characteristics in both the devices used in this work and for external clients. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:DXN041915 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Recommended from our members
Characterization of Thermal Regimes of Side Channels, Alcoves, and Ponds on the Willamette River, OR
No full textThe thermal regime of rivers plays a key role in aquatic ecosystem health. In the Willamette River, OR, the present day main channel temperature is often too warm for cold water fishes during the late spring, summer, and early fall. At these times, cold water fishes tend to be concentrated in cold water refuges, legally defined as having temperatures at least 2 °C cooler than the mainstem, and typically found in secondary channel features. These include side channels, ponds, and alcoves, the last being connected to the main channel only at their downstream ends.
To determine the processes that control the thermal regime of secondary channel features on the Willamette River, we used temperature measurements from 1 side channel, 8 alcoves, and 6 beaver ponds. Monitoring stations formed a three-by-three array of thermistors at upstream, mid-, and downstream distances along each feature at near-bed, middle, and near-surface depths. Channel geometry, flow velocity, shade, and dissolved oxygen were also measured.
Field measurements and aerial photographs yielded calculations of 3 dimensionless quantities, 1) Richardson, 2) advection, and 3) hyporheic numbers. The Richardson number is the ratio of buoyancy to flow shear, describing stratification. Values below 0.25 characterize a well-mixed water column. Two of our sites, the side channel and an alcove with significant surface water flow, were well-mixed. The advection number is the ratio of a relative heating (or cooling) flux from upstream to incoming solar radiation; it is a function of depth for points within stratified features, where “relative” fluxes are calculated from differences between temperature at points in the alcove or pond and the mainstem. At points where temperatures are cooler than the mainstem (e.g. near the bed), our advection numbers were negative (-6035 < Ad < 0). Likewise, positive advection numbers (0 < Ad < 3027) described points warmer than the mainstem (e.g. near the surface).
Near-bed temperature measurements for all stratified alcoves and ponds served to ground-truth our calculated values of the hyporheic number. More predictive than descriptive, the hyporheic number is a ratio of a cooling flux from hyporheic discharge to incoming solar radiation. The cooling flux reflects estimated lengths and hydraulic conductivities for the inferred subsurface flow path as well as the mean annual mainstem temperature (11.3 °C on the Willamette). Hyporheic numbers for stratified alcoves and ponds were all positive. With the exception of 1 beaver pond, all sites with a hyporheic number ³15 had locations cooler than the mainstem. Furthermore, a plot of advection number vs. hyporheic number produces a linear fit with R2 = 0.91.
On the Willamette River, secondary channel features that provide cold water refuges are characterized by 1) stratification, and 2) cool hyporheic discharge. Stratification is a necessary yet insufficient condition for cold water. Additionally, alcoves or ponds that do meet the legal requirement for a cold water refuge may be anoxic, as suggested by dissolved oxygen point measurements at 2 of our alcoves. Even so, the predictive hyporheic number has the ability to classify the thermal regimes of secondary channel features based on aerial photographs, gage measurements, and minimal field measurements. Ultimately, these calculations have the potential to guide both floodplain preservation and restoration efforts in a more quantifiable direction
Recommended from our members
Trace metal concentrations in the signal crayfish, Pacifastacus leniusculus (Decapoda: Astacidae), and the stonefly Pteronarcys californica (Plecoptera: Pteronarcyidae) along a downstream gradient of the Umatilla River
No full textMetals are a persistent form of freshwater pollution and have been shown to bioaccumulate in aquatic macroinvertebrates through direct contact with contaminated water, sediments, and through consumption of contaminated organisms. This research explored the longitudinal bioaccumulation patterns of 5 common trace metals (Cr, Cu, Zn, Cd, and Pb) in the signal crayfish, Pacifastacus leniusculus, and stonefly Pteronarcys californica along the mainstem Umatilla River. The Umatilla River drains a largely agricultural basin in northeastern Oregon and spans 140 kilometers from its headwaters in the Blue Mountains to its confluence with the Columbia River near Hermiston.
Crayfish concentrations of Zn and Pb, and to a lesser degree Cr, were significantly correlated with river distance, but contrary to expectations, concentrations decreased in the downstream direction. Cu and Zn were unrelated to river distance. Concentrations of Cr, Pb, and to a lesser degree Cd, were also significantly, negatively associated with crayfish carapace length, which was used as a proxy for age. Larger, older crayfish had lower concentrations, suggesting growth dilution. ANCOVA was used to test for effects of gender and mesohabitat on crayfish metal concentration after accounting for river distance and carapace length as covariates. Male crayfish had significantly higher Zn, Cd, Pb, and Cr concentrations than females, but absolute differences were fairly small. A significant difference in crayfish Pb concentrations between mesohabitats was found, with slightly higher concentrations in runs than riffles. Crayfish Cu concentrations were not correlated with any of the morphological, physicochemical, or spatial variables measured in this study. Due to their small size, metal concentrations in stoneflies were only measured in a single composite sample at each site, and stoneflies were only found at 7 of the upstream river sample sites. As a result, this small dataset was suggestive, but not conclusive, of relationships between stonefly metal concentrations and other variables. For both crayfish and stoneflies, none of the sampled metals appeared to clearly correlate with suspected point source or potential diffuse metal inputs.
This study also examined habitat associations of P. leniusculus by life history stage. Microhabitat scale differences in collection methods were found, with nonrandom methods (kick sampling and boulder flipping) resulting in a significantly higher number of crayfish captured than the random method (kick sampling). Using PCA, an exploration of microhabitat scale characteristics associated with P. leniusculus by size group found that crayfish with carapace length >20 mm were significantly associated with deeper water, higher percentages of organic matter and riparian cover, and higher water velocity. Distinct differences in habitat association also existed among three juvenile size groups. The smallest, youngest juvenile size group (carapace length <10 mm) showed a low association with velocity, percent organic matter, and percent riparian cover; the middle juvenile size group (carapace length 10-15 mm) was negatively associated with water depth; the largest juvenile size group (carapace length 15-20 mm) was comparatively less negative in its association with water depth, and more positively associated with velocity, percent organic matter, and percent riparian cover
Performance of the Bowen ratio systems on a 22 deg slope
No full textThe Bowen ratio energy balance technique was used to assess the energy fluxes on inclined surfaces during the First ISLSCP Field Experiment (FIFE). Since air flow over sloping surface may differ from that over flat terrain, it is important to examine whether Bowen ratio measurements taken on sloping surfaces are valid. In this study, the suitability of using the Bowen ratio technique on sloping surfaces was tested by examining the assumptions that the technique requires for valid measurements. This was accomplished by studying the variation of Bowen ratio measurements along a selected slope at the FIFE site. In September 1988, four Bowen ratio systems were set up in a line along the 22 degree north-facing slope with northerly air flow (wind went up the slope). In July of 1989, six Bowen ratio systems were similarly installed with southerly air flow (the wind went down slope). Results indicated that, at distances between 10 to 40 meters from the top of the slope, no temperature or vapor pressure gradient parallel to the slope was detected. Uniform Bowen ratio values were obtained on the slope, and thus the sensible or latent heat flux should be similar along the slope. This indicates that the assumptions for valid flux measurements are reasonably met at the slope. The Bowen ratio technique should give the best estimates of the energy fluxes on slopes similar to that in this study
Open Angle Glaucoma Effects on Preattentive Visual Search (PAVS) Efficiency for Flicker, Motion Displacement and Orientation Pop-out Tasks
No full textBackground/aim: Preattentive visual search (PAVS) describes rapid and efficient retinal and neural processing capable of immediate target detection in the visual field. Damage to the nerve fibre layer or visual pathway might reduce the efficiency with which the visual system performs such analysis. The purpose of this study was to test the hypothesis that patients with glaucoma are impaired on parallel search tasks, and that this would serve to distinguish glaucoma in early cases. Methods: Three groups of observers (glaucoma patients, suspect and normal individuals) were examined, using computer-generated flicker, orientation, and vertical motion displacement targets to assess PAVS efficiency. The task required rapid and accurate localisation of a singularity embedded in a field of 119 homogeneous distractors on either the left or right-hand side of a computer monitor. All subjects also completed a choice reaction time (CRT) task. Results: Independent sample T tests revealed PAVS efficiency to be significantly impaired in the glaucoma group compared with both normal and suspect individuals. Performance was impaired in all types of glaucoma tested. Analysis between normal and suspect individuals revealed a significant difference only for motion displacement response times. Similar analysis using a PAVS/CRT index confirmed the glaucoma findings but also showed statistically significant differences between suspect and normal individuals across all target types. Conclusions: A test of PAVS efficiency appears capable of differentiating early glaucoma from both normal and suspect cases. Analysis incorporating a PAVS/CRT index enhances the diagnostic capacity to differentiate normal from suspect cases
Interdisciplinary tool for optimizing agricultural production and erosion: a conceptual model
No full text
- …
